Tumor metastasis is the principal cause of death for cancer patients including breast cancer patients. Amplification/overexpression of the human neu protooncogene is correlated with the number of axillary lymph nodes positive for metastasis in breast cancer patients. Studies on the relationship between oncogene and metastasis would give new prospects for understanding the molecular mechanisms and cellular processes of cancer metastasis. The long term goal of this proposal is to understand how neu oncogene contributes to metastasis in breast cancer patients, hence develop effective preventative therapeutic reagents for neu oncogene-induced metastasis in breast cancer patients. In this proposal, we will first focus on the rat neu-transformed 3T3 model system; since our previous studies have demonstrated that neu oncogene can lead to higher metastatic potential in this system. Then we will study the role of human neu oncogene in breast cancer cell metastasis with similar approach. The Specific Aims of this Proposal are: 1. Elucidation of the role of neu gene in metastasis. We will treat Nu/Nu mice with antibodies against the extracellular domain of the rat neu encoded protein and shown to exert anti-tumor effects in vivo in experimental metastasis assays with the rat neu oncogene transformed 3T3 cells and compare the differences in the frequency of metastases in injected mice with or without the anti-neu antibodies. 2. Determination of the effects of E1A on the metastatic potential of neu-transformed cells. The adenovirus E1A gene products have been shown to repress neu expression and inhibit metastases of ras-transformed cells. We will compare the metastatic potential of neu transformed 3T3 cells with neu + E1A 3T3 transfectants (generated by P.I. from previous studies). 3. Examination of relationships between the neu gene and NM23 gene in neu transformed 3T3 cells. NM23 gene is a recently characterized metastasis suppressor gene. We will examine the expression of nm23 and neu in 3T3 cells, neu transformed 3T3 cells and neu + E1A transfectants by means of Western blot and Northern blot analysis to see if these genes might regulates each other or their functions might interact with each other. 4. Investigation of the role of neu oncogene in breast cancer cell metastasis. We will apply similar approaches described in Specific Aims 1,2, and 3 to human breast cancer cells that are metastatic and overexpress neu.